Lung adenocarcinoma with EGFR 19Del and an ALK rearrangement benefits from alectinib instead of an EGFR-TKI: A case report

Rationale: A remarkable concurrence of an EGFR mutation and an EML4-ALK fusion (double positive) occasionally occurs within a narrow number of patients. Previous studies using targeted therapy on EGFR/ALK co-mutated patients have commonly focused on single tyrosine kinase inhibitors (TKIs) or on the sequential use of EGFR-TKIs and ALK-TKIs. At present, no consensus exists regarding the treatment of patients with double positive mutations. The effectiveness of precision therapy also remains unknown. Patient concerns: A 53-year-old female non-smoker who described recurrent coughing and blood in her sputum over a month-long interval was examined at a local hospital. Diagnosis: Using computed tomography (CT) and positron emission tomography CT (PET-CT), the patient was diagnosed with Stage IVb lung adenocarcinoma (T4N3M1). Interventions: The patient had a novel ALK-RAB10 rearrangement identified using DNA sequencing, which, at the transcript level, was actually a canonical ALK fusion that caused a response to alectinib therapy. Outcomes: The patient has achieved partial remission (PR), with a progression free survival (PFS) of 16 months, and continues to benefit. Lessons: Our results may indicate differential sensitivities to TKIs in patients harboring an EGFR mutation and an ALK rearrangement. Our patient’s response to alectinib, instead of to EGFR-TKIs, may lead to an expanded list of alectinib beneficiaries who have rare gene co-alterations in lung adenocarcinoma.


Introduction
Over the past few years, multiple genomic breakpoints in fusion variants have been detected using DNA sequencing. Li et al [1] determined rare fusion variants identified using DNA-based next generation sequencing (NGS) that did not generate expressed fusion or canonical fusion transcripts. The result suggests the potential unreliability of genomic breakpoint locations in predicting biological outcomes. As such, to guide optimal treatment, additional validation using RNA-based NGS, immunohistochemistry (IHC), and fluorescence in situ hybridization (FISH) should be performed in uncommon genomic breakpoint fusion cases.
The coexistence of an EGFR mutation and an EML4-ALK rearrangement (double positive) has occasionally been determined in a narrow number of patients. [2][3][4] Currently, no unified opinion exists regarding therapeutics for patients with double positive alterations. Studies have shown that during the prealectinib era, EGFR inhibition was an integral part of treatment for patients with EGFR/ ALK co-alterations, whereas ALK inhibition via crizotinib has been shown not to display a more dramatic therapeutic effect. [5][6][7] Here, we report a case concurrently harboring an EGFR 19Del mutation and an ALK fusion (a novel ALK-RAB10 rearrangement identified using DNA sequencing that is actually a canonical ALK fusion at the transcript level), which yielded a positive response to alectinib therapy. Based on the effectiveness achieved by alectinib, increasing evidence supports the notion that alectinib, as an ALK-TKI, may be more effective than EGFR-TKIs in cases displaying the coexistence of an EGFR mutation and an ALK rearrangement (double positive).

Case presentation
In February 2018, a 53-year-old, female nonsmoker who described recurrent coughing and blood in her sputum over a month-long interval was examined at a local hospital. Using computed tomography (CT) and positron emission tomography CT (PET-CT), the patient was diagnosed with Stage IVb lung adenocarcinoma (T4N3M1). Two lesions (8.9 cm × 5.3 cm × 4.2 cm and 6.0 cm × 3.3 cm × 4.4 cm) were detected within the left lung, in addition to multiple lymph node and brain (1.5 cm × 1.4 cm) metastases (images not provided). The patient received 6 cycles of domestic pemetrexed (0.8 g) plus intravenous lobaplatin (50 mg) every 3 weeks from March to August 2018. The patient was then transferred to our hospital for further diagnosis and treatment. In November 2018, a chest CT and brain magnetic resonance imaging (MRI) revealed a 5.4 cm × 3.0 cm mass within the left lower lobe of the lung, a 3.2 cm × 3.2 cm mass within the left lower hilar, a 0.8 cm × 0.9 cm mass within the left parieto-occipital junction area, and mediastinal lymph node metastasis. Based on results from hematoxylin and eosin staining, as well as IHC (Fig. 1A), the pathological diagnosis was again confirmed as lung adenocarcinoma (T4N3M1, Stage IV).
A needle biopsy specimen was additionally sent to OrigiMed (Shanghai, China) for NGS analysis.
The NGS analysis revealed a novel ALK-RAB10 rearrangement and an exon 19 deletion of EGFR at the DNA level (Fig. 1B,C). To validate the location of the breakpoint, as well as the fusion partner at the transcript level, RNA-based NGS was performed. Interestingly, the actual fusion partner of the patient was EML4-ALK (Fig. 1D). Given the exon 19 deletion for EGFR, the patient began receiving 16 cycles of domestic pemetrexed (0.9 g) plus intravenous gefitinib (250 mg) every 3 weeks from November 2018 to February 2020 (Fig. 1E).
For the first 6 weeks of treatment, disease remained stable. However, following 16 cycles of Pem plus G treatment, the lesion in the lower lobe of left lung and lesion in the left lower hilar began to increase in size (5.2 cm × 3.5 cm and 5.0 cm × 4.8 cm, respectively), indicating disease progression. Due to the EML4-ALK fusion, in February 2020, the patient began alectinib treatment (600 mg, twice per day). Since April 2021, the patient has achieved partial remission (PR), with a progression free survival (PFS) of 16 months, and continues to benefit ( Fig. 1E and F).

Discussion
EGFR/ALK co-alterations and the ALK rearrangement of an uncommon genomic breakpoint were determined as the actual canonical fusion. Both occurrences are very rare in lung adenocarcinoma. Procedures for treating patients with concomitant EGFR/ALK co-alterations are sometimes controversial. Zhou et al [6] first reported that a lung adenocarcinoma patient with an EGFR-mutant and an ALK fusion acquired resistance to osimertinib, but was sensitive to the combined treatment of gefitinib plus crizotinib. Schmid et al [8] stated that EGFR-TKIs may display better outcomes, as compared to ALK-TKIs, in patients with an EGFR mutation and an ALK rearrangement. However, Won et al [9] reported the opposite and stated that ALK-TKIs may be preferred in patients with concomitant EGFR/ALK alterations. Qin et al [5] recently reported that a female lung adenocarcinoma patient with brain metastases and the coexistence of an EGFR mutation/DCTN1-ALK translocation responded well to successive osimertinib and alectinib treatment. These limited studies may indicate that patients harboring both an EGFR mutation and an ALK rearrangement exhibit different sensitivities to both types of TKI therapies, suggesting different degrees of dependence on EGFR and ALK oncogenes. [10,11] Our interest in this case arose from the fact that this case is the first report of a durable, dramatic response to alectinib in a lung adenocarcinoma patient harboring both an EGFR mutation and an ALK rearrangement for the uncommon genomic breakpoint. For a co-altered patient, the total PFS achieved using an ALK-TKI treatment was longer than the PFS achieved when using an EGFR-TKI treatment. A nearly complete response was also achieved with alectinib (a PFS of 13 months vs a PFS of 18 months). Such a discrepancy may indicate that the proportion of ALK amplification, as an oncogene driver, is higher than that of an EGFR mutation, or that the application of alectinib is more effective than EGFR-TKIs in the treatment of co-mutated lung adenocarcinoma patients.
Although a recent study also reported that alectinib was an effective treatment in patients with a co-mutation, [5] at present, we are still unable to draw definite conclusions. Our study suggests that additional validation using RNA-based NGS, IHC, or FISH should be performed for uncommon genomic breakpoint fusion. Based on our results to date, a subgroup of patients with a coexisting EGFR mutation and an ALK fusion may benefit from the treatment outlined.

Conclusion
The case presented provides a new reference for understanding ALK fusion mutations. Using DNA sequencing, we identified a novel ALK-RAB10 rearrangement within a lung adenocarcinoma patient that is actually a canonical ALK fusion at the transcript level. We also discussed the possibility for the future application of alectinib as an ALK-TKI for lung adenocarcinoma patients having an EGFR mutation and an ALK rearrangement (double positive). Despite our findings, at this stage, drawing clear conclusions regarding clinical characteristics and patient treatment outcomes is difficult. Long-term follow-up for the patient described in our study is ongoing, and we will continue to pay close attention as to whether alectinib resistance develops over time.